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Absorbing Aerosols, Possible Implication to Crop Yield - A Comparison between IGB Stations
R. Latha1, B.S. Murthy1, K. Lipi2, Manoj K. Srivastava3, Manoj Kumar4
1 Indian Institute of Tropical Meteorology, Pune 411008, India
2 Centre of Excellence in Climatology, Ranchi 835215, India
3 Banaras Hindu University, Varanasi 221005, India
4 Central University of Jharkahnd, Ranchi 835205, India
- BC radiative forcing at two stations in IGB compared.
- Solar radiation attenuated by at least 4–5% at any time of the day.
- BC aerosols reduce solar radiation by 25% during day break.
- Possible wheat crop yield loss estimate in winter is about a quintal per hectare.
The current study compares black carbon radiative effects at the densely populated plain station, Varanasi and the lesser populated plateau station Ranchi with large forest cover but with numerous open coal mines. While the measured average black carbon mass density (BC) reduces from February to March at Ranchi following an increase in convective mixing, it is observed to increase by 150% from February to March in Varanasi, as transport from northeast forest fires increases. It is observed that absorption due to black carbon of non-fossil fuel origin is prevalent throughout the day, in Varanasi, while this contribution is most significant during post sunset hours in Ranchi. Radiative forcing, estimated hourly using chemical model (to derive BC-aod) and radiative transfer model, indicates that at least 5% of the incoming radiation is always cutoff during any time of the day in Varanasi while this is about 4% in Ranchi. BC effectively causes an apparent delayed sunrise by reducing the incoming radiation on the plains of Indo Gangetic Basin (IGB) by up to 25% at the daybreak. An estimate of crop loss due to cut off in radiation, using an empirical formula for crop yield as a function of radiation, indicates a possible loss of more than a quintal per hectare considering anthesis (February) and maturity (March) periods for the winter wheat in both the IGB stations with consistently higher losses in Varanasi.
Black carbon; Radiative forcing; Biomass burning; Coal mines; Crop loss.